Exposing digital forgeries by detecting inconsistencies in lighting

ABSTRACT

When creating a digital composite of, for example, two people standing side-by-side, it is often difficult to match the lighting conditions from the individual photographs. Lighting inconsistencies can therefore be a useful tool for revealing traces of digital tampering. Borrowing and extending tools from the field of computer vision, we describe how the direction of a point light source can be estimated from only a single image. We show the efficacy of this approach in real-world settings.

REFERENCES

• 1: R. Brunelli. Estimation of pose and illuminant direction for face processing. Image and Vision Computing, 15(10):741--748, 1997.
• 2: W. Chojnacki and M. J. Brooks. Revisiting Pentland's estimator of light source direction. Journal of the Optical Society of America, 11(1):118--124, 1994.
• 3: James D. Foley , Andries van Dam , Steven K. Feiner , John F. Hughes, Computer graphics: principles and practice (2nd ed.), Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1990
• 4: J. Fridrich, D. Soukal, and J. Lukáš. Detection of copy-move forgery in digital images. In Proceedings of DFRWS, 2003.
• 5: J. Lukáš, J. Fridrich, and M. Goljan. Determining digital image origin using sensor imperfections. In Proceedings of the SPIE, volume 5685, pages 249--260, 2005.
• 6: P. Nillius and J.-O. Eklundh. Automatic estimation of the projected light source direction. In Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition, 2001.
• 7: Y. Ostrovsky, P. Cavanagh, and P. Sinha. Perceiving illumination inconsistencies in scenes. Technical Report AI Memo 2001-029, Massachusetts Institute of Technology, 2001.
• 8: A. Pentland. Finding the illuminant direction. Journal of the Optical Society of America, 72(4):448--455, 1982.
• 9: J.-M. Pinel, H. Nicolas, and C. L. Bris. Estimation of 2D illuminant direction and shadow segmentation in natural video sequences. In Proceedings of VLBV, pages 197--202, 2001.
• 10: A. C. Popescu and H. Farid. Exposing digital forgeries by detecting traces of resampling. IEEE Transactions on Signal Processing, 53(2):758--767, 2005.
• 11: A. C. Popescu and H. Farid. Exposing digital forgeries in color filter array interpolated images. IEEE Transactions on Signal Processing, (in press), 2005.
• 12: Jonathan R Shewchuk, An Introduction to the Conjugate Gradient Method Without the Agonizing Pain, Carnegie Mellon University, Pittsburgh, PA, 1994
• 13: P. Sinha. Perceiving illumination inconsistencies. In Investigative Ophthalmology and Visual Science, volume 41/4:1192, 2000.

INDEX TERMS

Primary Classification:
  I. Computing Methodologies
  I.4 IMAGE PROCESSING AND COMPUTER VISION
      I.4.m Miscellaneous

General Terms:
Security

Keywords:
digital forensics, digital tampering